False positive and exclusion not working

After an update to my NIS 2014 a few days ago, it's now reporting - over and over again - as malware a program that has been on my computer for at least two years and was never been flagged before. Scans with other anti-malware don't report any problems.

Telling NIS to exclude the file from scans has no effect - NIS keeps reporting it. This is whether I invoke the exclude option from the report (choose 'exclude' instead of 'fix', or exclude the whole folder where the program is located from being scanned in the settings.

NIS has all current updates installed.

What can I do to fix this?

NIS 22.5.4.24 Windows 7 64-bit.